1. Field of the Invention
This invention relates to a vehicle identification system, and particularly relates to a vehicle identification system applicable to the electric toll collection (ETC) systems provided with a means for measuring the location of a vehicle by measuring direction of arrival (DOA) of radio wave transmitted from the vehicle.
2. Description of the Related Art
A conventional vehicle identification system to be applied to ETC systems for using on toll roads is disclosed in U.S. Pat. No. 5,440,109. In this conventional vehicle identification system, an infrared beacon (IRB) which is a component of an infrared communication system (IRK), an infrared video camera (IRV) which is a component of an infrared location measurement system, a traffic radar system (RD), and a usual video camera (NV) which is a component of a vehicle identification-recording system (FIR) are installed on a toll booth side. These systems are connected to a controller for performing a total data processing and correlative processing.
By way of the data fusion of three types of information obtained from these systems, namely radar information, IR location information, and video information, the identification of a vehicle under the communication for toll collection is performed.
However, in this conventional vehicle identification system, it is required to install an infrared communication system, and it results in high cost. The communication by way of infrared ray is not appropriate to a foggy environment, and therefore if this conventional vehicle identification system is used in a foggy place, it is apt to cause the erroneous detection of a vehicle and communication trouble between a toll booth and vehicles.